This invention relates to stunning tongs for use in abattoirs for stunning animals prior to slaughtering them by any conventional methods such as bleeding as by cutting the throat or humane killer slaughter.
The stunning tongs of the present invention, while applicable for use with other animals such as sheep and cattle, are primarily for stunning pigs, and for doing so prior to slaughter. The slaughter of a pig is a specialized operation different from the slaughter of other animals in that the corpse should be drained rapidly of all blood immediately on slaughter to obtain the desired meat condition.
Slaughter is effected by suspending the animal by its hind legs and severing blood vessels in its throat to release the blood. It is desirable that the heart be beating at that time so that it pumps blood quickly out of the body. During this bleeding operation it is desirable for the body to be completely relaxed and without nervous tension. Otherwise the body would be stiffened by the muscles being in tension and might kick violently even though lifeless. This would cause blood clots and would also cause splashing of the blood from the body, and hence there would not be a steady quick drain of the blood from the body which is important if the meat is to be of high quality.
It would additionally be desirable that the body not bleed from any other point than the throat, especially not from the head, because too slow a bleeding flow would be established and blood splashing would result.
From the foregoing it will be apparent that the aniamal must be alive and relaxed at slaughter. However, for humane reasons, it must be completely insensible so that it will not suffer.
Stunning tongs are known (see U.K. Specification Pat. No. 364,386) comprising a pair of stunning arms carrying stunning heads and pivoted together to enable the arms to be spread apart to embrace any part of the head area of the animal and apply pressure thereto, the arms having handles for manual manipulation enabling the stunning heads to be engaged on either side of the animal's head. When the stunning heads are engaged on the animal's head an electric impulse is passed between them to stun the animal.
Such known stunning tongs are difficult to operate as well as being time consuming in use and the electric impulse is selected at random so that the tongs are not as efficacious as is desirable for satisfactory humane slaughter of animals.
It has been found that to achieve a satisfactory body state after stunning and before slaughter there is an optimum relationship between the firm contact of the stunning arms on the animal's head and the waveform/frequency and voltage/current of the electric impulse at the moment of impact as well as the time period of the application of the tongs on the head and the impulse in order effectively to stun the animal.
In the case of the apparatus of United Kingdom Specification Pat. No. 364,386 a harness is produced for application to a head of the animal. The harness works on the basis of the electrodes being pressed manually against the animal's head so that thereafter an electric charge or impulse can be passed through the animal's head to effect a stun and the kill. The harness itself is hand operated so that during application of the harness the animal becomes aware of what is being done and thus it subjects the animal to distress and tension prior to stunning or slaughter.
One prior proposal set forth in U.S. Pat. No. 3,163,884 contemplates the provision of stunning tongs which can be forced against the animal's head by electrically operated mechanical means, but the actual stunning heads are such as to penetrate the animal's head. The purpose of penetration is to ensure good electrical contact with the flesh of the animal and effectively to grip the animal so that contact will not be lost if the animal moves. This is prior to passing the stunning impulse so that there is a time lag between application of the tongs and passing the stunning impulse so that the animal is aware of what is being done prior to stunning. Moreover, an extremely high and potentially dangerous, for a hand-operated apparatus, voltage range of 750-950 volts is contemplated and such a voltage would in fact stimulate the animal's body so that it would be in a highly stiffened state during the stun which is unacceptable particularly for pigs.
Because of the skin penetration by the electrodes, the animal could move before the actual killing impulse is passsed, and any such movement of the animal would result in the animal being highly stressed in its nervous system and the skin of the head being damaged so that blood splashing will result.
In modern abattoirs pigs are placed in a restrainer which consists of a downwardly tapering trough which lifts the animal off its feet and then feeds it forward so that its head projects. The stunning is then carried out and the stunned animal is moved onto a table from which it is immediately picked up by its rear legs(s) and the animal's throat blood vessels severed over drip pans which collect the escaping blood. In this method there is a time delay of sufficient duration for the animal to react into tension before it is stunned.